Apparatus for cleaning heat exchangers and tube bundles



1962 G. E. OHMSTEDE 3,061,294

APPARATUS FOR CLEANING HEAT EXCHANGERS AND TUBE BUNDLES V FIG.].

INVENTOR GENE E. OHMSTEDE ATTORNEY5 Oct. 30, 1962 G. E. OHMSTEDE 3,061,294

APPARATUS FOR CLEANING HEAT EXCHANGERS AND TUBE BUNDLES Filed Sept. 16, 1960 2 Sheets-Sheet 2 FIG. 4. FIG. 3.

INVENTOR r: GENE E OHMSTE DE ZM g% MM) ATTORNEYS United States Patent Qflice 3,061,294 Patented Oct. 30, 1962 tion of Texas Filed Sept. 16, 1960, Ser. No. 56,469 8 Claims. (Cl. 26343) This invention relates to a cleaning apparatus, and in particular, to an apparatus adapted to clean heat exchangers, tube bundles, and other chemical processing equipment which are fouled with various polymers, synthetic resins, rubber compounds, and the like.

The upkeep and maintenance of chemical processing equipment, such as heat exchangers, is a major economic expenditure in the chemical processing industry, and diverse efforts have been directed to the cleaning of chemical processing equipment in a more rapid and efficient manner in order to avoid undue delay in placing the equipment back in operation.

A particular area of the chemical industry wherein this problem is of considerable importance relates to the cleaning and otherwise defouling of heat exchangers, tube bundles, and the like, which are fouled with pop corn polymers, various rubber compounds, monomeric materials that have polymerized, and solid materials generally having a burning or melting point in the order of approximately 600-900 F. These compounds are generally insoluble in ordinary solvents such as benzene and carbon tetrachloride, and cleaning by mechanical method-s, and such conventional solvents are largely ineffective.

For these reasons, new processes have been developed, for example, as set forth in the patent to Utsinger 2,563,- 085, which teaches a method of igniting various polymers in a controlled atmosphere of flue gas and air, to effectively burn off these deposits on chemical processing equipment.

It accordingly is an object of my invention to provide a new and improved apparatus for cleaning chemical processing equipment, such as heat exchangers, which have become fouled with various polymeric materials, rubber compounds, and the like, by igniting and burning off, or otherwise melting these undesirable materials, under controlled conditions.

A further object of my invention is to provide an apparatus for cleaning heat exchangers and the like, by igniting and burning the deposits thereon, which have an ignition point in the order of approximately 600-900 F., in controlled atmosphere of flue gas and oxygen.

Yet another object of my invention is to provide a cleaning apparatus, adapted for the controlled ignition and burning of solid chemical compounds of the nature described, by a new and improved means for controlling the conditions under which the burning takes place.

Still another object of my invention is to provide a closed cycle cleaning apparatus employing a regenerative gas means, with provision for close control of the oxygen content of the gas, for controlling the burning rate of the undesirable chemicals on heat exchangers and the like.

Further objects and advantages of my invention will become apparent with reference to the foregoing description and the appended drawings wherein:

FIGURE 1 shows a perspective view of the apparatus embodying certain features of my invention.

FIGURE 2 is a plan view of the apparatus shown in FIGURE 1.

FIGURE 3 is a full section elevational view of the furnace and related equipment used in my invention.

FIGURE 4 is a section view taken along line 44 of FIGURE 3, and

FIGURE 5 is a schematic plan view of the apparatus wherein the various control means for operation thereof are shown.

There is provided in this invention a closed cycle apparatus wherein flue gas is generated in a furnace and transmitted to an oven into which a fouled heat exchanger is placed for cleaning. Means are provided for regulating the percentage of oxygen in the flue gas atmosphere within the oven together with controls for regulating the temperature and pressure within the oven.

Referring now to FIGURE 1, there is shown an apparatus 10 comprising a furnace 12 and an oven 14. The furnace 12 is connected to the suction side of a conventional blower 16 by means of duct 18. The blower 16 is driven by a motor 17 through a conventional belt drive 19 operatively disposed between the drive shaft of the motor 17 and the driven shaft of the blower 16. The blower has its discharge duct 20 communicating with a manifold 22 which is disposed along a side Wall 24 of the oven 14. The manifold is in communication with the interior of the oven 14 by means of a plurality of pipes 26. The communication is further provided between the oven 14 and the furnace 12 for returning the gas from the oven 14 to the furnace 12 by means of an oven discharge duct 28.

The oven 14 has an appropriate door '30 at one end thereof for receiving a heat exchanger 32 which is disposed on an appropriate cart 32, riding on a track 34. The oven 14 is preferably an airtight enclosure when the door 30 is secured by appropriate means (not shown).

Suitable pressure relief valves or the like (not shown) are provided on the oven, to prevent an excessive rise of pressure therein.

Gas to be ignited in the furnace 12 is introduced into a preamixer 40 which is, in turn, in communication with the underside of furnace 12 by means of pipe 42. The gas is discharged into the furnace 12, ignited and discharged through nozzle 44, as clearly shown in FIG- URE 3.

The furnace is of generally cylindrical construction having side walls 46 terminating in an inverted conical section 48, and thence to discharge duct 18. Appropriate bricking 49 is provided about the inside surface thereof. A vent stack 50 extends upwardly from the furnace 12, as shown in FIGURE 1. The furnace 12 is supported by stanchions 52 which are secured to the furnace, as by welding. Within the furnace and extending upwardly from the bottom 54 is a cylindrical chamber member 56 of brick, construction having a staggered bricking. arrangement whereby passageways 58 are provided com municating with the furnace interior. The furnace is further provided with means for returning the flue gas from the oven 14 to the underside of the furnace as by an annular duct 60 which communicates with the return duct 28 and the inside of the furnace. The duct 60 is secured to the underside of the furnace by conventional techniques as by welding. The inner wall 61 of duct 60 extends upwardly well into the furnace and is in abutment with the outside surface of chamber 56, preferably to a point above the nozzle 44 of gas inlet line 42. It may, therefore, be seen from the arrows in FIGURE 3 that the flue gas, upon returning to the furnace 12 through return duct 28 and annular duct 60 is mixed with the burning flue gas emitted from nozzle 44, which passes through passages 58 in the chamber 56. Of course, additional baflling may be provided to suitably mix the return flue gas with the newly ignited flue gas.

Referring now to FIGURE 5, the apparatus is shown with the controls associated therewith. The oven 14 is shown with a heat exchanger 31 mounted on a cart 32 which, in turn, is located on track 30. Disposed in or on the tubes of heat exchanger 31 are a number of thermocouples 62 which communicate with a temperature recorder 64. A conventional multi-point temperature recorder such as Leeds and Northrop Speedomax Type G has been found to be suitable for this purpose.

A 'gas sampling pipe 66 is disposed in communication with the interior of the oven 14 for sampling the oxygen content of the atmosphere within the oven. This sampling pipe 66 is in communication with an oxygen analyzer 68 which provides an indication of the oxygen content in the flue gas atmosphere.

Preferably, an oxygen analyzer responsive to the magnetic permeability of the oxygen is used, as such a device affords highly accurate indications of the oxygen concentration within the oven 14. An oxygen analyzer as described in Richardson Patents 2,658,384; 2,728,217; and 2,658,385 has been found to be particularly efiicient in this regard. An air supply line 70 is provided with an appropriate valve 72 thereon for controlled admission of air into the oven, through duct 18 to provide oxygen thereto, the valve 72 being controlled by a signal 'generated in the oxygen analyzer 68 through an appropriate control line 73. The valve 72 is of conventional type, which may take the form of a solenoid valve actuated by an electric signal transmitted through the line 73. A steam source '74 is also provided with communication to the interior of oven 14 from duct 18, as by steam supply pipe 76 having a valve 78 therein.

There is thus provided for the controls of this apparatus: temperature indicating means, air supply means, oxygen analyzing means, steam supply means, and regenerative flue gas supply in a closed system.

Operation Reference will now be made to the operation of the apparatus to properly clean a heat exchanger which has become fouled with various polymers, rubber compounds and the like.

A heat exchanger 31 is placed on a cart 30 which is moved into the oven 14 on tracks 34. Approximately ten thermocouples 62 are preferably secured to the heat exchanger in various positions to provide a representative reading of the temperature on the surface of the heat exchanger 31 by temperature recorder 64.

The door 30 is then closed and the motor 17 is started, which, in turn, operates the blower 16. Steam is admitted into the oven by opening the valve 78, which admits steam into duct 18 from steam line 76, to remove any explosive gases in the oven 14. The steam supply is then shut off and the furnace 12 is placed into operation with gas being supplied to the underside of the furnace from a preamixer 40. The ignited gas is introduced into the chamber 56 from nozzle 44 of the oven 14 and out through duct 18. The gas is discharged from duct 18 into the oven 14 through blower discharge duct 20, manifold 22 and oven inlet pipes 26. The flue gas is recirculated back to the furnace 12 by means of duct 28 which communicates with the underside of the oven 14 through annular duct 60. The line gas is mixed with the newly ignited gas in the oven by the provision of the staggered brick construction of the inner chamber 56 which provides for passages 58 communicating with the oven.

The temperature within the oven is brought up to approximately 500600 F. at a rate of about 50 F. per hour, as will be indicated on the temperature recording meter 64. This temperature rise is properly controlled by regulating the flow of the gas from the premix burner 40 to the furnace 12.

The oxygen content of the atmosphere within the oven is preferably maintained at no more than approximately concentration. This oxygen content is regulated by the sampling of the oxygen content and recording thereof on oxygen analyzer 68. The air flow and the consequent oxygen content within the oven is regulated by valve 72 which provides the necessary flow of oxygen within the oven through air supply pipe 70. If the oxygen content becomes too high, valve 52 may be merely shut off for a time, as the recirculation and ignition of the flue gas will necessarily lower the oxygen content; and, conversely, if the oxygen content is too low the valve 72 may be opened wider and properly regulated to maintain the proper concentration of oxygen. In view of the fact that the apparatus is of a sealed construction, after the initial setting of the valves 72, there is relatively little regulation required to maintain the appropriate oxygen content within the oven 14.

When the temperature of the oven reaches approximately 800 F., the premix burner 40 is adjusted so as to maintain this temperature for approximately ten hours or until all the fouling material in the tube bundle is burned off. If the temperature of the tube bundle rises excessively, the oxygen content may be decreased as previously described, or, in an emergency, steam may be admitted to the oven by opening valve 78, which will provide an immediate cooling of the heat exchanger 31.

Toward the end of the burning period, additional air is admitted to the oven 14, and if the temperature of the heat exchanger does not rise as would be indicated on the temperature recorder, it can be assumed that all fouling material has burned off the tube bundle. The gas supply to the pre-mixer 40 is then shut off, the fan 16 continuing to circulate the heated fiue gas through the system. After the temperature of the heat exchanger 31 drops to approximately 300 F., the oven doors 30 are opened, and the tube bundle 31 may be removed from the oven when the temperature drops to approximately 200 F. This cooling cycle from 800 F. to 200 F. takes approximately ten hours, depending, of course, on the size of the heat exchanger. A temperature drop of about 50 F. per hour during the cooling cycle is not so excessive as to distort or warp the tubes in the heat exchanger. Steam may be emitted to the oven 14 on the cooling cycle to assist in reducing the temperature therein. Additionally, the steam can be emitted to the oven to reduce the temperature in the oven if the chemical material burns at an accelerated rate, whereby danger of metal failure would otherwise result due to excessive temperatures on the surface of the heat exchanger. It has been found that such a heating-holding-cooling cycle takes approximately 35 to hours depending on the size of the bundle and the degree of fouling.

The controls for the apparatus are preferably mounted on a control board, and the valves used herein may be remotely operable by solenoid means or the like, which are well-known in the art.

While the preferred embodiment of my invention is described herein, various modifications will be apparent to one skilled in the art, and therefore the disclosure should be considered in a descriptive and not in a limiting sense, when consideration is given to the foregoing claims.

What is claimed is:

1. An apparatus for cleaning chemical processing equipment which has become fouled with organic materials, polymers and the like comprising: an oven for reception of the equipment, a flue gas generator, means for supplying gas to said flue gas generator, means for recirculating flue gas between said oven and said generator including fan means associated therewith for imparting a super-atmospheric pressure to said oven, means for detecting the percentage of oxygen within said oven, oxygen supply means for said oven, means responsive to a pre-determined oxygen content within said oven for controlling said oxygen supply means to said oven, and means operatively disposed within said oven for measuring the temperature of the equipment therein.

2. An apparatus defined in claim 1 wherein said flue gas generator includes a closed housing having a stack,

and said gas supply means includes a pre-mix outside said housing, and a nozzle mounted within said housing and in communication with said pre-mixer.

3. Apparatus defined in claim 1 including means for introducing steam into said oven for cooling the equip ment placed therein.

4. Apparatus defined in claim 1 wherein said flue gas generator includes baflle means therein for mixing recirculated flue gas with newly generated flue gas, said recirculating means including an annular duct positioned in communication With the lower end of said flue gas generator, and a feed duct in communication with the upper end of said flue gas generator and in communication with said fan means.

5. Apparatus defined in claim 4 wherein said flue gas generator is of cylindrical construction and said annular duct is mounted in co-extensive relationship with the bottom thereof, said flue gas generator including a frustro-conical upper wall communicating at its upper end with said feed duct.

6. Apparatus defined in claim 4 wherein said baflie means includes a centrally disposed upright stack mounted adjacent the bottom of said flue gas generator, said stack having apertures within the side walls thereof and said gas supply means is in communication with the interior of said stack.

7. Apparatus defined in claim 1 wherein said recirculating means includes an inlet manifold mounted along the bottom region of a Wall of said oven to provide an even distribution of line gas throughout the length thereof and duct means at the upper end of said oven for returning flue gas therefrom to said flue gas generator.

8. Apparatus defined in claim 1 wherein said oxygen supply means includes an air line connected to the suction side of said fan means, said controlling means including an oxygen analyzer operatively connected to said oven, valve means in said air line responsive to the signal of said oxygen analyzer to open and close said valve means, and steam supply means communicating with the suction side of said fan means for selectively introducing steam in said oven for cooling the equipment placed therein.

References Cited in the file of this patent UNITED STATES PATENTS 1,365,422 Meroney Jan. 11, 1921 1,957,932 Berolzheimer et al May 8, 1934 1,979,639 Rebber et al Nov. 6, 1934 2,040,328 Olson May 12, 1936 2,110,209 Engels Mar. 8, 1938 2,475,077 Clancy July 5, 1949 2,563,085 Utsinger Aug. 7, 1951 2,607,576 Harter Aug. 19, 1952 2,769,693 Bearer Nov. 6, 1956 

